Newbie

[whinmoor]

Make sure you buy better solar panels than the inverters - I am not impressed with your inverter selection.

Time and time again I see people with little knowledge, taking shortcuts to install cheap solar systems, cutting corners, buying crap hardware, metaphorically shooting themselves in the foot, thinking they have bought a good system, ending up with a poor underperforming system that could have been so much better if they had took the time to consult a few experts on this forum like Earthstore.

If in doubt, ask and we'll try to help.

Eversolar make decent inverters. If they didn't, they wouldn't have just been taken over by SMA:

"SMA have taken over 72.5% of Eversolar (Zeversolar). This move brings additional solidity to the Eversolar brand, and allows SMA to benefit from world leading technical ability of Eversolar. With this joint venture, SMA is securing access to the growing Chinese market and is strategically consolidating its position as global market leader. The combination of the power of the SMA organisation combined with the technical ability of Eversolar ensures that Eversolar are the strongest value inverters in the U.K. market."

Whether it's the best choice for this particular job is, of course, another story...

 

[Gavin A]

Eversolar make decent inverters. If they didn't, they wouldn't have just been taken over by SMA:

"SMA have taken over 72.5% of Eversolar (Zeversolar). This move brings additional solidity to the Eversolar brand, and allows SMA to benefit from world leading technical ability of Eversolar. With this joint venture, SMA is securing access to the growing Chinese market and is strategically consolidating its position as global market leader. The combination of the power of the SMA organisation combined with the technical ability of Eversolar ensures that Eversolar are the strongest value inverters in the U.K. market."

Whether it's the best choice for this particular job is, of course, another story...

That's far more about SMA needing a way in to the massively growing chinese market if they wanted to stay as world number 1.

Not that I know anything particularly bad about eversolar, and you're probably right to an extent that SMA wouldn't buy a company that was properly dodgy.

 

[Steve_rutland]

I did look into this ( with my limited knowledge ) and was happy with the efficiency of the unit. This is a system built on what is basically a tiny buget. Having joined this forum ( bit late in the day I admit ) I have learnt a lot and I appreciate everyone's input. What I am trying to achieve is not the norm, but most of the kit I have, was purchased by trying to unscramble info on the Internet. All I can say is, had I joined earlier, things may have been different.

 

[Vegelen]

My last post was probably a little unfair.
You are educating yourself, doing the best you can to install a reasonable solar pv system on a limited budget.
You've pre-emptively bought inverters, before really understanding how to properly design a solar system.
Solar design is important to maximise the long term generation of an installed system.
If a poorly installed system underperforms by 20% (for example), that is a lot of lost energy and FIT payments over a 20 year period.
Gavin A, and many other members on this forum have got extensive experience in this field.
They've designed lots of solar systems and installed lots of kit.
Many of these systems are monitored to evaluate output.
They know the wheat from the chaff.
In many instances these companies can save their customers lots of money "long term".
There are some benefits to doing things yourself- you learn alot, make mistakes and gain knowledge.
The disadvantages with installing your own chosen solar kit is that if you make poor choices, it is a pretty big investment to get things wrong and long term you'll be stuck with a poorly designed underperforming system.
Many people on this forum give lots of free, impartial advice to help people, without the hard sell, hoping that some of these people may use their valued services and employ them to do what they know best.
Sometimes it can get frustrating reading these forums, when you see people make certain choices, thinking they are doing the right thing, when they could have saved themselves a mistake by proceeding with a little more caution - doing a little more research / asking for help.
I premptively judged your post, preverbially shot the gun- my cumulative frustrations after reading multiple examples of people trying to install cheap poorly designed solar systems, getting the better of me.
Good luck with your install- just do yourself a favour and politely ask a few experts, what system they'd install in your cirumstances and why.
Their answers will benefit you long term, in contrast to mistakes through inexperience which may cost you long term.

 

[Earthstore]

The importance or system design.

What you really need is an inverter that will be running at it's sweet spot for most of the time, and one that starts up with relatively low input from the panels therefore runs for longer every day, of course the weather each day is different in the UK so you can not get it perfect.

Now your panels are 3.5KWP per roof, the max they will produce under STD (standard test conditions) without any losses, but you do have losses, cables(correctly sized this are kept to a minimum), inverter, dirt on panels(I know you can clean them but not every day), orientation, degradation of panels over time, etc etc.

If your system was south facing your size of inverter would be about right, but yours is East/West, so the sun will be lower in the sky morning/afternoon whilst shinning on your panels.

Your system will most likely peak at around 2.5KW per array IE morning and afternoon on a perfect day, as your inverter is a 3.2KW it will take more power to start up than a smaller one per array and not be running at it's sweet spot, also when the sun goes around to the other side it is likely to shut down as there would not be enough power to keep it running.

If you were to choose something like an SMA TL5000 which has two inputs for different orientations, (or maybe a little smaller TL4000 maybe) then in the morning if the east is performing well then whatever the west is producing, no matter how small would be added to the easts figure, instead of having to wait for the sun to come around to generate enough power to fire up your 3.2 inverter.

You do also have to take into account panel voltage/ inverter voltage so that they are matched for output, this is a little more complex on a split system on different orientations and these parameters can be changed in some inverters by an expert, however they are factory set for a reason.

I personally like split systems like yours as it gives you a much more usable power curve for a longer period compared to a south facing which sees a very high peak midday, and overall, if designed well will produce almost as many KWH's per year.

If you are going to stick with your inverters then wire them close together leaving enough cable so you can change to one correctly calculated inverter in the future.

I believe I have stated before, this is an investment for 20 years, so if you can design a system that will produce a little more power every day compounded by 20 years, you will reap the rewards.

I have not mentioned your make of inverter, but I guess you know what my thoughts are.

 

[Steve_rutland]

Thanks again guys. Sooo wish i'd got on here sooner. Will certainly take on board your ideas to try and future proof it. Just coming back to voltages, is it best to have my total panel voltage as close to my inverter max voltage so it kicks in sooner ( which is what i think you're saying Kevin?) or go for a slightly higher voltage panel and split it into 2 strings?

 

[SibertSolar]

Difficult to give a definitive answer to be honest Steve. What I will say is that string voltages do not fluctuate much with changes in irradiance, current does but voltage doesn't. This means that the "power" from a string will vary with with irradiance and, as such, this is why an inverter's MPP tracking capabilities/parameters is important when configuring your strings. Optimum efficiencies are achieved when the inverter is tracking power curves that are driven from a voltage that sits in the MPP voltage range of the inverter. As such, try to keep your string voltage within this MPP range, taking into account a variation above/below the STC string voltage for differences in temperature, irradiance and air pressure (focus on temp really to be honest..).

Earthstore touched on a valid point above, in terms of inverter performance in the UK climate. Often manufacturers/resellers/installers talk about "low-voltage start-up" of an inverter. What they should really talk about is "low-power start-up" as this is really what's important. The voltage of a string will pretty much always be present, fluctuating with temp/irradiance/pressure a little as mentioned already. However, it's the current in the cell/module/string that fluctuates the most with irradiance - hence it's the power output that really matters and an inverter that can harvest yield from a very low power level is more important that one that has a particularly low minimum MPP voltage. Important not to get confused between minimum MPP voltage and "low-power start-up"......

Anyway, I'm rambling, good luck with your configuration, I have no direct experience with your particular inverters but I would hazard a guess that they have some sort of configuration tool/software - I would suggest you use that to determine your ideal string configuration for the particular panels you are using.

 

[Earthstore]

I have edited my post Andy, silly mistake there.
Your post is very informative, and I hope this thread will help others that are trying to choose a quality installer, as trying to design and install your own system is really not recommended, not if you want it to perform as well as it can do for any given situation.

 

[Steve_rutland]

You're not wrong there lol! I definitely wouldn't recommend anyone doing what I've done/am doing. It's a minefield for a novice and I'll be the first to admit, I'd have had a much better system had I been able to afford to go down the installer route.

 

[SibertSolar]

Yep, and this is why the new "DTI" Guide for surveying and quoting for a Solar PV system is effectively a carte-blanche for unscrupulous "designers" to offer the cheapest of the cheap inverter/panel combo's whilst still showing a base-line performance forecast that is no different to a higher VALUE solution offered by a more credible and quality-conscious provider! Dumbing down the industry and promoting cost-focused solutions in an attempt to give credence to DECC's "costs will continue to fall" mantra is NOT necessarily the way we need to go, in my humble opinion.....short-sighted to say the least....

Rant over...back to the grind-stone...

 

[Vegelen]

Poorly Designed / Installed Solar Pv Systems Cost Customers "Long Term":

System A:
Generated £1250 in FITS in 456 days (£2.74 per day average).

System B:
Generated £1250 Fits in 335 days (£3.73 per day average).

- System B generates 99p more per day in FITS, than System A, £361.75 less per year.
- System B will make £9043.75 more than system A over 25 years!
- Good solar designers generate higher FIT payments for their clients long term!

 

[Steve_rutland]

Wow! That puts it into perspective! Have taken your advice and popped a PM off :clap:

 

[Vegelen]

Solar PV is not a gold rush investment for "get rich quickers", it is a sensible, long term investment with large initial capital outlay which generates money slowly over a very long period of time, with an associated benefit - your long term electricity bill significantly reduces to, as you use some of the power you generate.

 

[Steve_rutland]

Yes, my plan is (hopefully) that the install will effectively pay the energy bills for the house, or at least put a good amount towards it. Had the structural survey done by the council yesterday and it's passed with flying colours, so that's another box ticked.

 

[AndyOz]

Any updates Steve?